Influence of Different Dietary Carbohydrates on Liver and Plasma Constituents in Rats Adapted to Meal Feeding

Abstract

Male Sprague-Dawley rats were given in one experiment diets with starch or sucrose and in a second experiment diets with glucose or fructose. In each experiment, one group of 5 rats was fed ad libitum and five other groups fed a 3-hour meal each day. After 36 days, one group of the meal-fed rats was killed when the meal was due, and the other groups at intervals after the beginning of the meal. The group fed ad libitum was killed the next day after 21 h fasting. Meal feeding led to a smaller food intake and a smaller gain in weight, and a lower blood concentration of triacylglycerol. The diets with sucrose or fructose produced heavier livers and kidneys than did those with starch or glucose. The consumption of the meal led also to a temporary increase in the weight of the liver. The weight of the kidney, however, did not change in rats given starch or gluocse, but fell in rats given sucrose or fructose. Meal consumption was also followed by an increase in the concentration of liver glycogen, irrespective of the nature of the dietary carbohydrate. The concentration of plasma fatty acids was affected differently by meals containing the different carbohydrates, the extremes being a continuing fall with starch and no change with fructose. The concentration of triacyglycerol was increased by sucrose or fructose after the presentation of the meal. The concentration of blood glucose rose and then fell when the meal contained starch or glucose, but fell and then rose when it contained sucrose, and especially when it contained fructose. The concentration of insulin in meal-fed rats receiving sucrose was higher than that of rats receiving starch, both before and after the meal. This difference was not seen in rats fed ad libitum. The results indicate that the effects of meal feeding, or of sucrose or fructose, are not additive.